Duophonic electrical musical instrument



Dec. 19, 1944. N. LANGER DUOPHONIC ELECTRICAL MUSICAL INSTRUMENT FiledMay 8, 1942 2 Sheets-Sheet l a ,N. M T T H.

Dec. 19,1944. NQLANGER 2,365,566

DVUOPHONIC ELECTRICAL MUSICAL INSTRUMENT Filed May 8, 1942 2Sheets-Sheet 2 INVENTOR. N/Cf/OL HS LHIVG'E/P HTTORNEY Patented Dec. 19,1944 DUOPHONI c 'nmc'rnrcar. MUSICAL ms'raumm'r Nicholas Lang-er, NewYork, N. Y., assignor to Central Commercial Company, Chicago, 111., acorporationof Illinois Application May 8, 1942, Serial No. $42,225

7 Claims. (Cl. 84-132) The present invention relates to electricalmusical instruments, and, more particularly, to an electrical musicalinstrument of the type in which space discharge tubes, suchas thermionicployed to denote instruments of the prior art in which one, or more,oscillation producing space discharge devices are employed in suchcircuit combinations as to produce only a singleimusical note at a timeupon depression of any single playing key. It is acknowledged thatinstruments of the monophonic type have obvious musical limitations, inthat they cannot produce harmonies or chords and can only carry a singlevoice or melody. As those skilled in the art know, with the exception ofthe piano, the harp, and the organ, practically all of the conventionalmusical instruments are of a generally monophonic character, althoughgreatly restricted and largely transient polyphonic eiiects may beproduced by most string instruments. Therefore, a substantial field ofmusical literature is available for interpretation by means ofmonophonic instruments, particularly if these instruments areaccompanied byother instruments of the conventional or electrical type.

With the development of the art of electrical musical instruments, ithas been found increasingly desirable to provide an electrical musicalinstrument which is capable of producing two musical notes at the sametime. An instrument of this type would have considerably less musicallimitations than the instruments of the menophonic type and in additionto interpreting a great portion of existing musical literature, variouspleasing and novel eil'ects could be obtained thereby. For convenience,in the following, the term duophonic will be employed to denote aninstrumentof this type, capable of producing two musical notes at thesame time from the same or common-keyboard. p

The simplest and most obvious way of obtaindescribed character ing aduophonic electrical instrument would be to combine a pair of monophonicinstruments in a single case, each of said instruments having its ownoscillation producing space discharge devices, sound producing means,and manually operative-elements, such as keyboards, for controlling thepitch of the notes produced. Considerable practical difliculties are,however, encountered in carrying'this concept into practice. First ofall, the duplication of all parts doubles the cost and the spacerequirements strument. Another and even more serious disadvantage isthat two playing manuals have to be provided, both of which have to besimultaneously operated by the player. This greatly increases thedimculty of playing as frequently the fingers of the same hand had to beplaying on diiferent manuals or keyboards, this obviously requiring suchmanual deiterity and training which, while available to is highlyskilled organist, is beyond the skill of the average music lover.

I have discovered that the outstanding problem may be solved in aremarkably simple manner with resultant musical advantages that havenever before been attained.

It is an object of the present invention to provide an electricalmusical instrument which avoids the foregoing difllculties andinconveniences, and which makes it possible to produce duophonic musicby, means of an extremely simple playing technique.

It is another object of the present invention to provide a duophonicelectrical musical instrument in which a pair of monophonic'electricalmusical instruments arecombined with a slngle playing manual or keyboardin such a manner that any two musical notes within the range of the twomonophonic instruments may be produced simultaneously.

A further and important object of the present invention resides in theprovision of an organization of parts, including an electrical networkand a common key-board, wherein upon simultaneous actuation of any twoplaying keys-one part of said electrical network automatically functionsto produce audible sound of the pitch of the note associated with one ofsuch keys, during similar production by another'part of said network ofaudible sound of the pitch of the note associated with another key,thereby causing a simultaneous audible production of tones correspondingto the musical frequencies oi notes associated with diflerent playingkeys of said common keyboard, substantially in the same manner as whentwo keys are simultaneously actuated in any well known instrument of theheretofore I mentioned polyphonic type.

The invention also contemplates a 'duophonic musical instrument which isextremely simple in construction and easy to manufacture and to operateand which may be readily manufactured and sold on a practical andcommercial scale at a price which i only slightly higher than that of amonophonic musical instrument.

Other and further objects and advantages of the present invention willbecome apparent from the following description taken in conjunction withthe accompanying drawings, in which Fig. 1 illustrates a circuit diagramof a preferred embodiment of the present invention in which gaseousdischarge tubes, such as, for example, glow-discharge tubes, neon tubes,and the like, are employed for producing electrical oscillations ofmusical frequencies; and

Fig. 2 depicts a similar circuit in which space discharge tubes of thethermionic type are employed for producing the electrical oscillationwithin the audible range which are ultimately converted into musicalsounds.

Broadly stated, according to the principles of my invention, I provide aduophonic electrical musical instrument in which a pair of monophonicoscillators are incorporated. Each of these oscillators comprises atleast one space discharge device electrically associated with electricalelementssuch as resistances, capacities. inductances of suitable valueand with switching means for selectively connecting such elements ofdifierent value to the space discharge device. Generally speaking, thetype of electrical elements employed and the method of their connectionwith the'switching means varies with the type of oscillator which isemployed. Thus, in gaseous discharge tube oscillators it is preferred toemploy resistances and capacitors of appropriate value to tune theoscillator to the desired pitch, while in thermionic tube oscillanotes,that is: notes not corresponding to any note of the tempered scale,produced. For example, when a chain of serially-connected resistors isused, the note actually produced will conform to the higher one of thetwo coordinated to the actuated pair of keys, while when a chain ofserially-connected capacitors is used. the note actually produced uponactuation of 'two keys or switching elements will'conform t 1 the lowerone of the two coordinated to the actuated pair of keys.

tors resistances and capacitors or inductances and capacitors ofpredetermined values may be employed to selectively tune the instrumentto any note within the musical range of the instrument. It has beenfound desirable to maintain one of the said elements fined, while theother one is adjustable in steps by means of the switching elements. Forexample, in the case of glow-discharge tube oscillators, a wide range ofmusical frequencies may be produced by connecting a capacity ofdetermined value to the tube and by connecting resistances of dlfierentvalues to such capacity. The same result may be obtained by connecting aresistance of deflnite value to the tube and connecting the same incircuit with capacitors of different value. Inthe first case the "keyedelement is the resistance in the other the capacity and to control thepitch of the oscillations produced, generally as many keyed elements areprovided as there are musical intervals within the range of theinstrument. It has been found that best results are obtained when thekeyed element is provided in the form of a chain of elements connectedin series 01' which one or more are rendered effective by actuation of asuitable switching key. The advantage of this arrangement is that whenit happens thatmore than one switching element is actuated at the sametime. only the switching element which is the lowest, (or highest) intheseries becomes effective, connecting the chain up to that point withthe O In the following the expressions high-responsive" andlow-responsive" will be appliedto the combination of a space dischargedevice with a network of tuning elements variable in steps by means ofkey-controlled switching elements when upon simultaneous actuation oiany two keys, the higher or the lower of the two will respectivelydetermine the frequency of the resulting oscillation.

In order to provide a duophonic electrical musical instrument, inaccordance with the principles of the present invention, afhigh-responsive and a "low-responsive monophonic oscillator withassociated switching elements are coordinated to a common playing manualin such a manner that each key of the playing manual has two switchingelements coordinated thereto, electrically associated with therespective monophonic oscillators. I have found that when in aninstrument of the described character any two keys are depressedsimultaneously. the two switching elements corresponding to the"highresponsive" oscillator will cause said oscillator to oscillate atthe higher frequency of the two, while the two switching elementscorresponding to the low-responsive oscillator will cause the saidoscillator to oscillate at the lower frequency of the two. In otherwords, upon depression of any two keys, two frequencies will beproduced, one oscillator automatically being assigned to the higher oneof the two and the other being automatically assignedto the lower one ofthe two, as it will be explained more fully as the description proceeds.It will be readily understood by those skilled in the art that certainelements of the two monophonic oscillators may be in common in order tosave space and mate because any change in the voltage of the currentsupply will substantially uniformly influence both monophonicoscillators.

The invention will now be explained morefullytothoseskilledintheart,referencebeing had to the accompanyingdrawings. in which certain preferred embodiments of my invention areillustrated.

now more particularly to Fig. 1 of the drawings. the simplified circuitof a duophonic electrical musical instrument employing two-electrodegaseous discharge tubes is shown. Reference character O-i generallydenotes a monophonic gaseous discharge tube oscillator comprising a tubeG-l having two electrodes, connected in series with a condenser C and asource of direct current voltage B-i, through the primaryv winding of anoutput transformer T. A serially connected chain of resistances R-I, R-2R-E is connected at one end to the common point of tube G-I andcondenser C and has normally open, key-actuated switches or key contactsS-l, 3-2 S-S between the other ends of the respective resistances and acommon bus bar D-l connected to the other plate of condenser C. Eachswitch is operatively connected with a key of the playing manual, switchS-l being connected with key K-I, switch 8-2 with key K4, and so forth.It will be noted that upon depression of each key, a predeterminednumber of the serially connected resistances is connected acrosscondenser C. Thus, upon depression of K-i, switch S-l is closed andresistance R-I will be connected across C, upon depression of K-2 bothserially connected resistances R-i and R-2 will be connected acrosscondenser C, etc. As those skilled in the art know, in a circuit of thedescribed character electrical oscillations will be produced, thefrequency of said oscillations being determined by the capacity and theresistance in the circuit, provided that the other factors havingbearing on the frequency such as the break-down and extinction voltagesof the tube and the voltage of current source B are maintained constant.By appropriate selection of C and of resistances R-l, R4, etc., it ispossible to produce frequencies corresponding to suecessive notes of thetempered scale. Preferably, resistances Rr-i; R4 R-i are adjustable inorder to facilitate tuning of the instrument to its proper pitch. It isalso advantageous to provide capacitor C in the form of a variablecondenser to adjust the general pitch of the device, experience havingshown that varying the capacity of C has the effect of varying thefrequency of the oscillations produced upon depression of any key bysubstantially the same amount without aphave been shown, obviously anydesired number of such tuning elements may be employed in accordancewiththe extent of the desired musical range. Thus, in practical. instrumentsit has been found desirable to use 31, or more, playing keys andassociated resistances, covering the range of three octaves, or more.

Although oscillator 0-! with its associated network of switches andresistances constitutes a monophonic electrical musical instrument andconsequently at any time only one key has to be depressed, in playing aninstrument of this type with the conventional playing technique familiarto players of keyboard instruments it is unavoid able that at times morethan one key is depressed at the same time. This seems to beparticularly the case in playing -legato passages when in order toobtain a closely knitted sequence or flow of successive notes, the nextkey is depressed already before completely releasing the last. Todetermine the effect of this occurrence. let us assume that first keyK-l is depressed and then key K4 is depressed, before releasing K-l. Thedepression of K-i will close switch S-l and will connect resistance R-lacross condenser C.

-This will tune oscillator 04 to its highest frequency in view of thefact that the lowest value of resistance will be connected into thecircuit. Assuming that now key K4 will be likewise depressed, this willclose switch S4 but will not change the amount of resistance connectedacross C, because resistances R-2 and R4 between switches S-l and 8-3are short-circuited by the corresponding portion of bus bar D-i. Inother words, in oscillator 0-! when more than one switching key isdepressed at the same time, the oscillator will be tuned to the highestof the frequencies corresponding to the depressed keys. In theterminology introduced in the foregoing, this may be expressed bystating that oscillator 04 is a high-responsive monophonic oscillator.

The oscillations produced by oscillator O-i may be taken off through atransformer T and may sistance R and with the source of direct current Bthrough the primary winding of transformer T, thesource of current andthe output transformer being in common with oscillator 04. A chain ofserially connected condensers 0-5.

C4 0-4 is connected at one end to the common point of resistance R andtube G-2. Switching keys or key contacts S-iil, S-9 8-6 are connectedbetween each common point between successive condensers and common busbar D-I whereby any desired number of serially connected condensers maybe connected across resistance R in accordance with the switch operated.Thus, it will be noted thatwhen key contact S-lli is actuated, condenser0-5 will be connected across resistance R which will cause oscillationsof musiof two condensers connected in series is lower corresponds to thefrequencies of successive notes I of the tempered scale. To facilitatesuch tuning of the oscillator, condensers 0-! to C-5 and also resistanceR, may be made adjustable. By

A adjustingcondensers C-l to C-J. the proper tuning of the oscillatormay be readily accomplished and each note may be readily brought intothe proper and desired pitch of the tempered scale I while by adjustingR, the general pitch of the ous notes. Of course, in a commercialinstrument a relatively large number of condensers and key contacts isused, such as, for instance 31, corresponding to the range of threeoctaves.

It is worth noting that in an oscillator of the described character inwhich a chain of serially connected condensers is employed, uponactuation of more than one key contact at the same time, always thefrequency corresponding to the lowest actuated key contact will beproduced. This will be readily understood from contemplation of thecircuit of oscillator -2 in Fig. 1. Assuming that key contact S-Hl isclosed, condenser 0-! alone will be connected across resistance R,tuning the oscillator to the lowest frequency of its range. When new keycontact 3-! is likewise closed, serially connected condensers C4, C4 and0-5 will be all connected across resistance R through bus bar D-2.However, the portion of the chain between contacts 8-8 and 5-", that iscondensers C-3 and (3-4, will be short-circuited through the saidcontacts and the said bus bar and will have no effect on the frequencyof the oscillations produced, such frequency being determined only bythe capacity of 0-5. In other words, in case more than one key contactis closed at the same time, the frequency of the'oscillations producedis determined by the key contact corresponding to the lowest frequencybetween the key contacts actuated, or reverting to the specialterminology introduced in the foregoing, an oscillator, such as 0-2,employing a condenser chain in series connection is a low-responsivemonophonic oscillator.

The oscillations produced by means of'oscillator 0-2 are-withdrawnthrough transformer T which is in common with oscillator O-l. Theseoscillations,together with the oscillations produced by means ofoscillator O-l are amplified by amplifler A-l and are converted intomusical sounds by means of translating device or loudspeaker L-l.

In the circuit constituting Fig. 1 of the drawing, a. high-responsive,"serially-connected resistance-tuned monophonic oscillator O-l iscombined with a low-responsive" serially-connected condenser-tunedmonophonic oscillator 04, both oscillators being supplied from a currentsource in-common and fceding their.output into a com- 7 mon amplifierand device. As it will I be likewise readily observed in Pig. 1, keycontacts 8-! to 8-! cause production of oscillations having step by stepdecreasing frequencies of the tempered scale, same as closure ofcontacts 8-! to S-l I, associated with oscillator 0-2. In view of thefact that the longer the chain of resistances R-l to 3-5, the higher theresultant resistance is, and.'on the other hand, the longer the chain ofserially-connected condensers, the lower the resultant capacity is,oscillators 0-! and 0-2 and their respective key contacts arecoordinated in reversed relative sequence. Thus, key contact 84 isdirectly W upon key contact 8-. key contact 8-! is-directly su rposedupon key contact 8-1, etc. In other words, key contacts of oscillators04 and 0-! are superposed upon each other in such an arrangement thatcontactscorresponding to the same frequencies are superposed upon eachother and may be actuated by the depressionof the same key of theplaying manual. This is indicated by means of'the dotted linesconnecting key contacts S-l and 8-0, 8-2 and 8-1 which may be closedsimultaneously by depression of keys K 4 and K4, respectively. Thismechanical connection may be readily secomplished by mountingcorresponding key contact sets directly underneath of the same key ofthe playing manual, as those skilled in the art will'understand withoutany detailed explanation.

From the foregoing description, the operation of my duophonic electricalmusical instrument will be readily understood. When any two keys of theplaying manual, or keyboard, are simultaneously depressed, two pairs ofkey contacts will be simultaneously closed, two of these contacts beingin the circuit of 04 and two of these contacts in the circuit of 0-2. Inview of the fact that oscillatorO-l with its chain of serially connectedresistances is a high-responsive" monophonic oscillator and oscillator0-2 with its chain of serially connected condensers is a low-responsive"monophonic oscillator, oscillator O-l will be tuned to the frequencycorresponding to the higher one of the depressed keys, while oscillator0-2 will be tuned to the frequency corresponding to the lower one of thedepressed keys. Thus, upon depression of any two keys of the playingmanual, the higher one of the two will be automatically assigned tooscillator 04 and the lower one will be automatically assigned tooscillator 0-2. The two oscillations simultaneously produced may beamplified by amplifier A-l, which is inductively coupled with bothosciloscillators.

lators, and may be rendered audible by means of translating device L-iwhich is likewise in common for both oscillators. Of course, it is quitepossible to provide separate outpu'qmeans, ampliners and translatingmeans for both oscillators but in most cases this is not necessary, nordesirable.

While generally the same musical range is assigned to both oscillatorsso that upon depression or any single playing key both oscillators aretuned to the same note of the tempered scale, in'

some cases further musically valuable results may be obtained by soadjusting the general pitch of the two oscillators that there is adefinite and constant interval therebetween. This interval may bethat'of an octave, of a fifth, a third, etc. and may be readily obtainedby proper adJust- ,ment of condenser C in oscillator O-l and or re-'sistnnceRinoscillator 0-2. In this case the de- Dression of any singlekey of the p aying manual will cause the production of two notes whichare separated from each other by the constant interval separating thegeneral pitchof the two oscillators, while upon deprusion of'any twokeys of the playing manual two notes will be heard which will beseparated from each other by the interval between the two playing keysPlus or minus the diflerence between the Whenstsnytimemorethantwokeyssre3 simultaneously depressed in m duophonicelectricsLonlythehlshestsndthelowestwillbesffcctive in determining thepitch of the two simultaneously heard notes while the intermediatekuswillhavenoeifectonthehmingofthelnstrument.

Pig. 2 illustrates a modifledembodiment of the principles of the presentinvention into a duo- Dhonic electrical musical instrument in whichthermionic tubes are employed for producing the electrical oscillationsof musical frequency. ,The ch'cuitdcpictedlnl'lg willbefolmdtobemwhsimilartothstshowninl'lg.1inthatahigh-' responsive" and s"low-responsive monophonic electrical musical instrument is combinedinto a single instrument with a common playin manusl or keyboard. Thehigh-responsive monogeneral pitch of the two are converted into musicalsounds by means of translating means L4 and L4, respectively. Thegeneral pitch of oscillators -3 and'O-4 may be adjusted by means ofvariable condenser C-l l and variable resistance R-II, respectively. Inthe simplest case the general pitch of both oscillators may be the same,or, if desired, any appropriate musical interval may be provided betweentheir general pitch, such as that of an octave, fif h. third, etc. Thevolume of the two oscillators m y be adjusted individually by means ofvolume control potentiometers P-2 and P-l, respectively,

' which may be combined in a single, collectively addusted unit, ifdesired.

Although the present invention has been described in connection with afew preferred embodiments thereof, variations and modifications may beresorted to by those skilled in the art without departing from theprinciples of the present invention. Thus, various refinements may beapplied to the monophonic oscillators to produce wave forms of modifiedshape and thereby simulate the tone quality of different instruments orto obtain tone color or timbres of novel and musically useful type,toincorporate tremolo, percussion and the like eifects. While themonophonic oscillators disclosedcomprise only a single space dischargedevice, the invention is also'applicable to oscillators of the type inwhich a plurality of space discharge devices tuned to harmonicallyrelated frequencies is employed to produce asingle musical note of thetempered scale at a time.

Instead of a chain of series-connected resistances, a tapped inductancemay be employed with equal, or similar, results, particularly in thecircuit disclosed in Fig. 2. I consider all of these variations andmodifications as within the true spirit and scope of the presentinvention, as disclosed in t e foregoing description and defined by theappended claims.

I claim:

l. A duophonic electrical musical instrument comprising in combination apair of electronic oscillators tunable in steps to frequencies within amusical range; each of said oscillators including a space dischargedevice, a'series of tuning elements, and a plurality of switches forselectively connecting portions of said series intooscillation-producing relation with said space discharge device; saidtuning elements and their associated switches being so connected incircuit that upon actuation of more than one switch at a time theoscillators are tuned to frequency s respectively corresponding to thehighest and to the lowest of the actuated switches; a playingfrequencies corresponding to successive notes of the tempered scalewithin a desired range; each of said oscillators including a spacedischarge device, a series of tuning elements, and a pinrality ofswitches for selectively connecting portions of said series intooscillation-producing relation with said space discharge device; said2,ses,sss

ated switches; a playing manual for operating said switches in pairsappertaining to different oscillators; sound producing means responsiveto the output of said oscillators; and individual means for adjustingthe general pitch and the amplitude of the-oscillations produced by eachoscillator.

3. An electronic musical instrument of the twin melody type whichcomprises in combination a pair of relaxation oscillators tunable insteps to frequencies corresponding to notes of a musical scale; each ofsaid oscillators including a glowdlscharge tube having only twoelectrodes, a tapped tuning element, and a plurality of switches forselectively connecting taps of said element into oscillation-producingrelation with said tube; the tapped tuning elements and their associatedswitches being so connected in circuit that upon simultaneous actuationof a plurality of switches the oscillators are tuned to a frequencyrespectively corresponding to the highest and to the lowest of theactuated switches; a playing manual for operating said switches in pairsappertaining to different oscillators; and sound producing meansresponsive to the output of said oscillators.

4. An electronic musical instrument of the twin melody type whichcomprises in combination a pair of relaxation oscillators tunable insteps to frequencies corresponding to notes of a musical scale; one ofsaid oscillators including a glowdischarge tube, a tapped resistanceelement, and a plurality of switches for selectively connecting taps ofsaid resistance element in oscillationproducing relation with said tube:the other of said oscillators including a glow-discharge tube, a tappedcapacitor element, and a second plurality of switches for selectivelyconnecting taps of said capacitor element in oscillation-producingrelation with said last-named tube; the taps of said resistance and ofsaid capacitor element and their associated switches being so connectedin circuit that upon simultaneous actuation oi a plurality of switchesthe oscillators are tuned to a frequency respectively corresponding tothe highest and to the lowest of the actuated switchs; a playing manualin common for both oscillators for operating said switches in pairsappertaining to diiferent oscillators; and sound producing meansresponsive to the output of said oscillators.

5. An electronic musical instrument of the twin melody type whichcomprises in combination a pair of relaxation oscillators; one of saidoscillators including a two-electrode glow-discharge tube, a pluralityof serially connected resistances. and a plurality of switches forselectively connecting a determined number of said resistances inoscillation-producing relation with said tube;

the other of said oscillators including a two-elem in: manual in commonfor both oscillators for tuning elements and their associated switches ibeing so connected in circuit that upon actuation of a plurality ofswitches at a time the oscillators are tuned to a frequency respectivelycorresponding to the highest and to the lowest of the actuoperating saidswitches in pairs appertaining to different oscillators; and soundproducing means responsive to the output of said oscillators.

6. An electronic musical instrument of the twin melody type whichcomprises in combination a pair or oscillators: each of said oscillatorsbeins independently tunable in steps to frequencies corresponding tosuccessive notes of the tempered 7 scale and including a space dischargedevice havaccuse ing at least a cathode, a grid and an anode, a seriesof tuning elements, and a plurality of switches for connecting adetermined number of said tuning elements in oscillation-producingrelation with said space discharge device; said tuning elements andtheir associated switches being so connected in circuit that uponactuation ot a plurality of switches at a time the oscillators are tunedto a frequency respectively corresponding to the highest and to thelowest oi. the actuated switches; a playing manual for operating saidswitches in pairs appertaining to difierent oscillators; and soundproducing means responsive to the output of said oscillators.

7. An electrical musical instrument comprising in combination a pair ofoscillators individually tunable in steps to frequencies correspondingto successive notes of the tempered scale and of the type in whichaudio-frequency oscillations are respectively corresponding to thehighest one and to the lowest one of the actuated switches; a playingmanual for operating said switches in pairs appertaining to differentoscillators; and sound producing means responsive to the output of saidoscillators.

NICHOLAS LANGER.

